Due to the popularity of the digital television, the resolution of the image is upgraded from 720*480 pixels (NTSC) to 1920*1080 pixels (Full HD). This increases the size of the flat panel display. However, the way of driving liquid crystals is not improved accordingly. Hence, the response time of the frame is increased, which results in the afterimage for the television. Therefore, an over-driving method has been proposed below to improve the above-mentioned drawback.
Please refer to FIG. 1(a), which shows the first liquid crystal response time driven by the driving voltage in the prior art. There are two curves in FIG. 1(a), wherein the upper curve represents the waveform of the input driving voltage 11 and the lower curve represents the optical response curve of liquid crystals 12. TF represents the time for a frame, the transverse axle of the waveform of the input driving voltage 11 represents the time, the vertical axle of the waveform of the input driving voltage 11 represents the voltage, the transverse axle of the optical response curve of liquid crystals 12 represents the time, and the vertical axle of the optical response curve of liquid crystals 12 represents the gray scale.
Please refer to FIG. 1(b), which shows the second liquid crystal response time driven by the over-driving voltage in the prior art. There are two curves in FIG. 1(b), wherein the upper curve represents the waveform of the input over-driving voltage 13 and the lower curve represents the optical response curve of liquid crystals 14. In FIG. 1(a), when the input driving voltage is VD, the first liquid crystal response time t1 is 3*TF. That is, it takes the time of three frames to reach the cut-off gray scale Grey 2 from the initial gray scale Grey1. However, in FIG. 1(b), when the input over-driving voltage is VOD which is larger than VD, the second liquid crystal response time t2 is TF. That is, it only takes the time of one frame to reach the cut-off gray scale Grey2 from the initial gray scale Grey 1. Although such driving method can reduce the response time of liquid crystals from t1 to t2, the liquid crystal panel cannot display normally when the vertical synchronization frequency of the television signal is larger than 60 Hz. Therefore, it is necessary to provide a method which can be used when the vertical synchronization frequency of the television signal is larger than 60 Hz.
In order to overcome the drawbacks in the prior art, a device for selecting an image processing function and the method thereof are provided. The particular designs in the present invention not only solve the problems described above, but also are easy to be implemented. Thus, the present invention has the utility for the industry.